{"id":4003,"date":"2025-07-28T21:33:24","date_gmt":"2025-07-28T13:33:24","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=4003"},"modified":"2025-07-28T21:33:24","modified_gmt":"2025-07-28T13:33:24","slug":"threadlocal%e4%bc%9a%e5%87%ba%e7%8e%b0%e5%86%85%e5%ad%98%e6%b3%84%e6%bc%8f%e5%90%97%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/07\/28\/threadlocal%e4%bc%9a%e5%87%ba%e7%8e%b0%e5%86%85%e5%ad%98%e6%b3%84%e6%bc%8f%e5%90%97%ef%bc%9f\/","title":{"rendered":"ThreadLocal\u4f1a\u51fa\u73b0\u5185\u5b58\u6cc4\u6f0f\u5417\uff1f"},"content":{"rendered":"\n<p>\u662f\u7684\uff0c<strong><code>ThreadLocal<\/code> \u53ef\u80fd\u4f1a\u51fa\u73b0\u5185\u5b58\u6cc4\u6f0f<\/strong>\uff0c\u8fd9\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\u662f\u4e00\u4e2a\u975e\u5e38\u5bb9\u6613\u88ab\u5ffd\u89c6\u4f46\u6781\u5176\u91cd\u8981\u7684\u95ee\u9898\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u53e5\u8bdd\u603b\u7ed3\uff1a<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong><code>ThreadLocal<\/code> \u672c\u8eab\u4e0d\u4f1a\u6cc4\u6f0f\uff0c\u4f46\u5176\u5f15\u7528\u7684\u5bf9\u8c61<\/strong>\u5982\u679c<strong>\u672a\u53ca\u65f6\u6e05\u7406\uff0c\u4f1a\u9020\u6210\u5185\u5b58\u6cc4\u6f0f\uff0c\u5c24\u5176\u5728\u4f7f\u7528\u7ebf\u7a0b\u6c60\u65f6\u66f4\u5bb9\u6613\u53d1\u751f\u3002<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001\u4e3a\u4ec0\u4e48 ThreadLocal \u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u6f0f\uff1f<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. <strong>ThreadLocalMap \u7684 key \u662f\u5f31\u5f15\u7528\uff0cvalue \u662f\u5f3a\u5f15\u7528<\/strong><\/h3>\n\n\n\n<p>Java \u4e2d <code>ThreadLocal<\/code> \u662f\u901a\u8fc7\u6bcf\u4e2a\u7ebf\u7a0b\u7684 <code>ThreadLocalMap<\/code> \u5b58\u50a8\u53d8\u91cf\u7684\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Thread\n \u2514\u2500\u2500 ThreadLocalMap\n       \u251c\u2500\u2500 Entry(key = ThreadLocal \u5f31\u5f15\u7528, value = \u771f\u6b63\u7684\u503c)<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>key \u662f <code>ThreadLocal<\/code> \u5b9e\u4f8b\u7684\u5f31\u5f15\u7528\uff08<code>WeakReference&lt;ThreadLocal&lt;?>><\/code>\uff09<\/strong><\/li>\n\n\n\n<li>\u5982\u679c\u5916\u90e8\u6ca1\u6709\u5f3a\u5f15\u7528\u6307\u5411\u8fd9\u4e2a <code>ThreadLocal<\/code> \u5bf9\u8c61\uff0c\u5b83\u5c31\u4f1a\u88ab GC \u56de\u6536<\/li>\n\n\n\n<li><strong>value \u662f\u5f3a\u5f15\u7528\uff0c\u6307\u5411\u4f60\u5b9e\u9645\u8bbe\u7f6e\u7684\u5bf9\u8c61\uff08\u5982\u6570\u636e\u5e93\u8fde\u63a5\u3001\u5bf9\u8c61\u6c60\u7b49\uff09<\/strong><\/li>\n\n\n\n<li>\u5373\u4f7f <code>key<\/code> \u88ab\u56de\u6536\uff0c<code>value<\/code> \u4ecd\u7136<strong>\u65e0\u6cd5\u56de\u6536<\/strong><\/li>\n<\/ul>\n\n\n\n<p><strong>\u8fd9\u5c31\u5bfc\u81f4\u4e86\u201c\u5b64\u513f value\u201d\u4e00\u76f4\u6302\u5728\u5f53\u524d\u7ebf\u7a0b\u4e2d\uff0c\u65e0\u6cd5\u91ca\u653e\uff0c\u4ea7\u751f\u5185\u5b58\u6cc4\u6f0f\u3002<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001\u573a\u666f\u590d\u73b0\uff1aThreadPool + ThreadLocal \u6cc4\u6f0f<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>private static final ThreadLocal&lt;byte&#91;]&gt; local = new ThreadLocal&lt;&gt;();\n\nExecutorService pool = Executors.newFixedThreadPool(1); \/\/ \u7ebf\u7a0b\u4e0d\u4f1a\u9000\u51fa\n\npool.execute(() -&gt; {\n    local.set(new byte&#91;10 * 1024 * 1024]); \/\/ \u6a21\u62df\u5927\u5bf9\u8c61\n    \/\/ \u6ca1\u6709\u8c03\u7528 local.remove()\uff01\n});<\/code><\/pre>\n\n\n\n<p>\u7531\u4e8e\u7ebf\u7a0b\u6765\u81ea\u7ebf\u7a0b\u6c60<strong>\u4e0d\u4f1a\u88ab\u9500\u6bc1<\/strong>\uff0c\u5e76\u4e14\u672a\u8c03\u7528 <code>remove()<\/code>\uff0c<strong>ThreadLocal \u7684\u503c\u4f1a\u5e38\u9a7b\u5185\u5b58\uff0c\u65e0\u6cd5\u88ab\u56de\u6536\uff01<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u5982\u4f55\u907f\u514d ThreadLocal \u5185\u5b58\u6cc4\u6f0f\uff1f<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u4e3b\u52a8\u8c03\u7528 <code>ThreadLocal.remove()<\/code><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>try {\n    local.set(obj);\n    \/\/ \u4f7f\u7528 ThreadLocal \u7684\u503c\n} finally {\n    local.remove(); \/\/ \u4e00\u5b9a\u8981\u6e05\u7406\uff01\n}<\/code><\/pre>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u5c24\u5176\u5728<strong>Web \u9879\u76ee\u3001\u7ebf\u7a0b\u6c60\u4e2d<\/strong>\uff0c\u5fc5\u987b\u4e3b\u52a8\u6e05\u7406\uff01<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u4f7f\u7528\u7ebf\u7a0b\u6c60\u65f6\u683c\u5916\u5c0f\u5fc3<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u7ebf\u7a0b\u6c60\u4e2d\u7684\u7ebf\u7a0b\u957f\u65f6\u95f4\u4e0d\u9500\u6bc1\uff0c<code>ThreadLocal<\/code> \u7684\u503c\u4e5f\u4e0d\u4f1a\u91ca\u653e<\/li>\n\n\n\n<li>\u5c3d\u91cf<strong>\u5728\u4efb\u52a1\u5b8c\u6210\u540e\u7acb\u5373 remove()<\/strong><\/li>\n\n\n\n<li>\u6216\u8005\u4f7f\u7528 <code>InheritableThreadLocal<\/code>\/\u5de5\u5177\u6846\u67b6\uff08\u5982\u963f\u91cc\u5df4\u5df4\u7684 TransmittableThreadLocal\uff09<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u4e0d\u8981\u7528 ThreadLocal \u5b58\u50a8\u8fc7\u5927\u7684\u5bf9\u8c61<\/h3>\n\n\n\n<p>\u4f8b\u5982\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4e0d\u5efa\u8bae\u5b58 <code>byte[100MB]<\/code>\u3001\u6570\u636e\u5e93\u8fde\u63a5\u3001\u6587\u4ef6\u53e5\u67c4\u7b49\u5927\u578b\u8d44\u6e90\uff1b<\/li>\n\n\n\n<li>\u53ef\u8003\u8651\u7528\u5bf9\u8c61\u6c60\u3001\u8fde\u63a5\u6c60\u7b49\u4ee3\u66ff\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001\u5173\u952e\u6e90\u7801\u7247\u6bb5\uff08\u6765\u81ea JDK 8\uff09<\/h2>\n\n\n\n<p><code>ThreadLocalMap.Entry<\/code> \u6e90\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>static class Entry extends WeakReference&lt;ThreadLocal&lt;?&gt;&gt; {\n    Object value;\n    Entry(ThreadLocal&lt;?&gt; k, Object v) {\n        super(k);\n        value = v;\n    }\n}<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u8bf4\u660e\uff1a<strong>key \u662f\u5f31\u5f15\u7528<\/strong>\uff0cGC \u540e\u4f1a\u53d8\u6210 <code>null<\/code>\uff0c\u4f46 value \u4f9d\u7136\u5b58\u5728<\/li>\n<\/ul>\n\n\n\n<p>\u5728 <code>ThreadLocalMap.set()<\/code> \u5185\u90e8\u4e5f\u6709\u6ce8\u91ca\u8bf4\u660e\u6b64\u95ee\u9898\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ We replace stale entries (where key == null) during set()\n\/\/ to prevent memory leak<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u5f00\u53d1\u5b9e\u6218\u5efa\u8bae<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u573a\u666f<\/th><th>\u5efa\u8bae\u5904\u7406\u65b9\u5f0f<\/th><\/tr><\/thead><tbody><tr><td>\u666e\u901a\u4e1a\u52a1\u7ebf\u7a0b\u4e2d\u4f7f\u7528<\/td><td>\u7528\u5b8c\u540e\u8c03\u7528 <code>ThreadLocal.remove()<\/code><\/td><\/tr><tr><td>\u7ebf\u7a0b\u6c60\u4e2d\u4f7f\u7528<\/td><td>\u5f3a\u70c8\u5efa\u8bae\u6bcf\u6b21\u4efb\u52a1\u7ed3\u675f\u540e <code>remove()<\/code> \u6e05\u7406<\/td><\/tr><tr><td>Web \u6846\u67b6\u4e2d ThreadLocal \u4f7f\u7528<\/td><td>\u914d\u5408\u62e6\u622a\u5668\/Filter \u5168\u5c40\u6e05\u7406<\/td><\/tr><tr><td>\u5b58\u50a8\u5927\u5bf9\u8c61<\/td><td>\u8c28\u614e\uff01\u5efa\u8bae\u7528\u5bf9\u8c61\u6c60 +\u7ebf\u7a0b\u5c01\u95ed\u5904\u7406<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u63a8\u8350\u9605\u8bfb<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u300aJava \u5e76\u53d1\u7f16\u7a0b\u5b9e\u6218\u300b\u7b2c 3 \u7ae0<\/li>\n\n\n\n<li>\u300aEffective Java\u300b\u7b2c 3 \u7248\uff1aItem 50\uff1a\u907f\u514d ThreadLocal \u6cc4\u6f0f<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/alibaba\/p3c\">\u963f\u91cc\u5df4\u5df4 Java \u5f00\u53d1\u624b\u518c\uff1a\u5173\u4e8e ThreadLocal \u7684\u5f3a\u70c8\u89c4\u8303<\/a><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u603b\u7ed3\u4e00\u53e5\u8bdd<\/h2>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><code>ThreadLocal<\/code> \u672c\u8eab\u4e0d\u4f1a\u5185\u5b58\u6cc4\u6f0f\uff0c\u4f46<strong>\u5982\u679c\u4e0d remove()\uff0c\u7ebf\u7a0b\u6c60 + \u5f31\u5f15\u7528\u673a\u5236 + \u5f3a\u5f15\u7528 value<\/strong>\u7684\u7ec4\u5408\uff0c\u5f88\u5bb9\u6613\u5bfc\u81f4\u4f60\u4ee5\u4e3a\u88ab GC \u7684\u5bf9\u8c61\u5176\u5b9e\u8fd8\u5728\uff01<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u662f\u7684\uff0cThreadLocal \u53ef\u80fd\u4f1a\u51fa\u73b0\u5185\u5b58\u6cc4\u6f0f\uff0c\u8fd9\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\u662f\u4e00\u4e2a\u975e\u5e38\u5bb9\u6613\u88ab\u5ffd\u89c6\u4f46\u6781\u5176\u91cd\u8981\u7684\u95ee\u9898\u3002 \u4e00\u53e5\u8bdd [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":4004,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-4003","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/4003","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=4003"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/4003\/revisions"}],"predecessor-version":[{"id":4005,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/4003\/revisions\/4005"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/4004"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=4003"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=4003"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=4003"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}